That's the satellite connector/cable for sirius xm antenna. I have the same connector in my SR. It comes from factory with the harness (taped on the side to the harness I believe). The only issue is the SR does not have the satellite antenna installed on the roof. But you have the wiring (from factory, believe it runs through the passenger side pillar and connects to the antenna there) in case you decide to upgrade your HU and install the oem satellite antenna.

Hope that helps. If you found any more info on it, please let me know. I would like to know where the wire leads to.. I'm in the process of my own upgrade.